1. Technical Field
The present disclosure relates to entering and leaving a motor vehicle freewheel (coast) running condition with internal combustion engine off.
2. Description of the Related Art
In order to reduce fuel consumption and pollutant emissions of motor vehicles during urban driving, automotive manufacturers are progressively introducing so-called “Stop & Start” systems in motor vehicles, which have the task of switching off the internal combustion engine when the motor vehicle is about to stop and traction power is no longer required, and in particular when the speed of motor vehicles drops below a minimum speed, currently between 0 and 10 km/h, depending on the manufacturer, and the gearbox is in neutral.
In order to further reduce fuel consumption and pollutant emissions in motor vehicles, it has been proposed to extend the operation of the Stop&Start system to motor vehicles equipped with a servo-actuated transmission, whether automatic or automated, so as to cause motor vehicles to freewheel with internal combustion engine off under special conditions. In particular, it has been proposed to stop the internal combustion engine and disengage the driveline, by disengaging the clutch, whenever the accelerator pedal is released or is not pressed for more than a given time interval, while the motor vehicle speed is less than a given speed higher than that used in Stop & Start systems, currently between 75 and 80 km/h, depending on the motor vehicle manufacturer, and then cranking the internal combustion engine and subsequently engaging the driveline, by engaging the clutch, with a speed ratio appropriate for providing the motor vehicle with traction power as soon as the accelerator pedal is pressed (again).
When the clutch is disengaged to cause the internal combustion engine switching off, the gear engaged at that moment can alternatively be kept engaged or be disengaged so as to cause the gearbox to be put into neutral. In this last case, the clutch can alternatively be re-engaged or expediently be kept disengaged, in this way reducing the wheels' drive load.
The internal combustion engine can be cranked up in various ways, in particular by inertial cranking, by fuel injection or by means of electric machines, such as the starter, which are connected to the internal combustion engine by means of belts or gears, and the way is chosen based on, amongst other things, the conditions of the motor vehicle, of the internal combustion engine and of the road (gradient, curve and grip), and on the driver's requests (pressure on the accelerator pedal, pressure on the brake pedal and use of the gearbox lever).